The present invention relates to a control unit for controlling the operation of a permanent-magnet-type synchronous motor equipped with a position sensor so as to drive the motor with rotation speed that is controlled. More particularly, the present invention relates to a control unit for of a permanent-magnet-type synchronous motor suitable for opening and closing doors of an electric train (such as dual-panel sliding doors of subway cars).
FIG. 3 is a block diagram showing an example of a conventional motor-control unit. The construction and operation of this control unit will be described below. Reference number 1 represents a 3-phase permanent-magnet-type synchronous motors, such as a linear motor for driving a door 2 so as to enable it to open and close. The door 2 includes a pair of door panels that are moved away from one another to open the door 2 and move toward one another to close the door 2. These door panels are linked to motor 1, and the opening and closing speed of the door 2 is proportional to the rotary speed of the motor 1. Power is supplied to the motor 1 from a power converter 3, consisting of an inverter or the like. Reference number 4 represents a power source such as a battery connected to the power converter 3. Reference number 6 represents a closed position-detecting sensor for detecting when the door 2 is fully closed and remains in the closed position. A closed-position detection signal generated by the sensor 6 transmitted to a speed-instruction arithmetic unit 10, which arithmetically processes a speed instruction value (or speed command valve) 10a for motor 1 based on a door opening-and-closing instruction 106. The speed instruction valve 106 is an analog signal having a level that is proportional to the desired opening or closing speed.
Reference number 5 represents a position sensor for detecting the actual magnetic-polar position of the motor, corresponding to the shaft-angle of the motor 1. The position sensor 5 may be an encoder outputting a square wave during 180 degrees of the three phases (UVW). The detection signal output from the position sensor 5 is transmitted to a motor-speed arithmetic unit 11 and a motor-position arithmetic unit 15. The motor-position arithmetic unit 15 arithmetically generates an actual magnetic-polar-position signal 15a and an actual door-position signal 15b, and the arithmetically processed door-position signal 15b is then transmitted to the speed-instruction arithmetic unit 10.
Reference number 12 represents a subtraction unit that computes the difference between a speed instruction valve 10a output from the speed-instruction arithmetic unit 10 and an actual speed value determined by the motor-speed arithmetic unit 11. Reference number 13 represents a speed adjuster that computes the propelling power or motor drive power needed to fully eliminate the difference. Reference number 14 represents a current-instruction arithmetic unit, which arithmetically processes current instruction values pertaining to d-axis and q-axis components in a “d, q” coordinate system, based on a propelling-power instruction value output from the speed adjuster 13.
Reference number 7 is a current detector for detecting the DC current supplied from the power converter 3 to the motor 1. Reference number 16 is a coordinate converter, which arithmetically processes the current at the coordinates “d and q” based on the detected current value and actual magnetic polar position data output from the motor-position arithmetic unit 15. Reference numbers 17 and 18 are subtraction units, which arithmetically process the difference between current instruction values related to d-axis and q-axis components that have been output by the current-instruction arithmetic unit 14, and the current detection values related to d-axis and q-axis components output from the coordinate converter 16.
The difference values output by the subtraction units 17 and 18 are then transmitted to a d-axis current adjuster 19 and a q-axis current adjuster 20, which respectively generate a d-axis voltage instruction value and a q-axis voltage instruction value so as to fully cancel each difference value.
The d-axis voltage instruction value and the q-axis voltage instruction value are transmitted to a polar-coordinate converter 21, which computes the magnitude of a voltage instruction vector and its phase, and the computed results are then transmitted to a voltage-instruction arithmetic unit 22. The unit 22 uses the voltage instruction vector and phase to generate signals to drive the converter 10 so as to produce AC drive current at phases U, V, and W for driving the motor 1.
Next, based on the voltage instruction vector output from the polar-coordinate converter 21 and the magnetic polar position data 15a output from the motor-position arithmetic unit 15, the voltage-instruction arithmetic unit 22 generates signals to drive the converter 10 so as to produce generally sinusoidal drive current at phases u, v, and w for driving the motor 1.
Reference number 23 represents a position-sensor abnormal-condition identifier, which identifies whether the signal output from the position sensor 5 is normal or abnormal. For example, an output of (L, L, L) or (H, H, H) from the position sensor 5 would be indicative of an abnormality. If an abnormality is identified, the identifier 23 causes the supply of power to the motor 1 via the power converter 3 to be halted or an appropriate alarm to be generated.
In the above constitution, when door 2 is closed, the speed-instruction arithmetic unit 10 storing the instruction for closing the door 2 computes the speed instruction value 10a for the movement of the door 2 to the closing position. As previously described, the movement speed of the door 2 is proportional to the rotation speed of the motor 1 driving the door 2, and the speed arithmetic unit 11 computes the actual speed by referring to the data output from the position sensor 5. Next, the speed adjuster 13 computes a propelling-power instruction value so that difference between the speed instruction value and the detected speed value can be canceled.
Based on the propelling-power instruction value from speed adjuster 13, the voltage instruction values are computed via the current-instruction arithmetic unit 14, subtraction units 17 and 18, and the current adjusters 19 and 20. Then, a voltage instruction vector is generated via the polar-coordinate converter 21. Next, the voltage instruction vector is converted into individual voltage instructions corresponding to each of the three phases by the voltage-instruction arithmetic unit 22, before eventually being transmitted to the power converter 3 so that the motor 1 can be driven.
The motor 1 is driven to move the door 2 to the closed position (for example) by causing the motor 1 to rotate at an rpm in pursuit of a speed instruction value output from the speed-instruction arithmetic unit 10. When the door-closing position-detecting sensor 6 detects that the door 2 has just arrived at the closing position, a door-closing detection signal is transmitted to the speed-instruction arithmetic unit 10 to cause the speed instruction value to be reset to zero.
In response, the power converter 3 discontinues the supply of power to the motor 1, thereby causing the door 2 to halt itself at the closed position.
When the door 2 is opened, the speed-instruction arithmetic unit 10 storing the door-open instruction computes a speed instruction value for the movement of the door 2 to the open position so as to enable the motor 1 to be driven via the same steps executed for closing the door 2. When the door position determined by the position arithmetic unit 15 has just arrived at the fully open position, the door speed-instruction arithmetic unit 10 resets the speed instruction value to zero. In response, the power converter 3 halts the supply of power to the motor 1, thereby causing the door 2 to stop at the fully open position.
When the position-sensor abnormality identifier 23 identifies that an abnormal signal has been output from the position sensor 5 while the door 2 is in the process of opening or closing, this in turn causes the controlling precision to be reduced, as the speed arithmetic unit 11 and the position arithmetic unit 15 can no longer determine a precise values for the motor's speed and magnetic polar position. In response, using the abnormality detection signal output from the position-sensor abnormality identifier 23, the power converter 3 discontinues the supply of power to the motor 1.
For reference, a controller with a construction substantially identical to that explained above is disclosed by Yoshihiko Satoh, et al., “On the development of a linear-motor-driven door system suitable for a commuter train”, (in translation), Treatise No. 114, Proceedings of the 1999 Japan Industry Applications Society Conference, The Institute of Electrical Engineers of Japan, 1999, pages 359-362.
In the above-cited prior art, whenever an abnormality in the output of the position sensor 5 is detected by the position-sensor abnormality identifier 23, the operation of the motor 1 is suspended. As a result, when the above prior art is applied to a sliding door 2 at the side of a car in an electric train, the operation for opening and closing the door must be suspended during opening or closing. As the door is not fully closed, unwanted delays will occur.